2
Version No. V5R0
Safety Manual
9202 Pulse Isolator
1. observed standards
2. acronyms and abbreviations
Acronym /
Abbreviation
Designation
Description
Element
Term defined by IEC 61508 as “part of a
subsystem comprising a single component
or any group of components that performs
one or more element safety functions”
PFD
Probability of
Failure on Demand
This is the likelihood of dangerous safety
function failures occurring on demand.
PFH
Probability of dan-
gerous Failure per
Hour
The term “Probability” is misleading, as IEC
61508 defines a Rate.
SFF
Safe Failure
Fraction
Safe Failure Fraction summarises the
fraction of failures which lead to a safe
state and the fraction of failures which will
be detected by diagnostic measures and
lead to a defined safety action.
SIF
Safety Integrity
Function
Function that provides fault detection (to
ensure the necessary safety integrity for the
safety functions)
SIL
Safety Integrity
Level
The international standard IEC 61508
specifies four discrete safety integrity levels
(SIL 1 to SIL 4). Each level corresponds to
a specific probability range regarding the
failure of a safety function.
Standard
Description
IEC 61508
Functional Safety of electrical / electronic / programmable
electronic safety-related systems
IEC 61508-
2:2000
Part 2: Requirements for electrical / electronic / programmable
electronic safety-related systems
IEC 61508-
3:1998
Part 3: Software requirements
IEC 61326-
3-1:2008
Immunity requirements for safety-related systems